CELL,
CELL MEMBRANE
AND
INTERCELLULAR
JUNCTION
Bakare, A. A.
-Cell is the basic
functional and
structural unit of
life
-Smallest unit
capable of
maintaining
independent life
BASICA STRUCTURE
Organelles
are
suspended
in the
cytosol
which is
embounded
by cell
membrane
STRUCTURAL COMPONET
Cell
Cell membrane
Cytoplasm
Organelles
Membranous
Non-membranous
CELL MEMBRANE
Cell membrane
or plasma
membrane or
cytoplasmic
membrane
It is a biological
membrane that
form cell boundary
or surrounds the
cell
FUNCTIONS
-Separates cell from external environment
- Protects the cell from invasion or attack
-Controls in the movement of molecules
across the cell
-Involves in a variety of cellular processes
such as cell adhesion, ion channel
conductance and cell signaling
STRUCTURE
 Phospholipd
bilayer
 Each
phospholipids
has a head
(hydrophilic) and
tail (hydrophobic)
region arranged
with the heads at
ends
Transmembrane Proteins
 Proteins
are imbedded
within the membrane
 They
are permanently
attached to the membrane
passing from one side of a
membrane to the other side
of the membrane providing
a channel through which
molecules and ions can
pass into the cell.
CYTOPLASM: CYTOSOL +ORGANELLES
- It is enclosed by the cell membrane.
-
The cytoplasm includes all of the
material inside the cell or outside of
the nucleus within the cell
(nucleoplasm).
-
It is made-up of ;
1. CYTOSOL
2. ORGANELLES
CYTOSOL


Jelly-like
and
colourless
substance
It is mainly
composed ;
water (80%)
 Salts
 Proteins.

FUNCTIONS OF CYTOSOL
-Cytosol holds the internal components of cells in
place
- Maintain cell shape
-Create cell Volume, because without it, organelles
might collide against each other, resulting in
damage
-Material transport
-Storage, liquid space such as vacuoles are form
and act as storage until these materials are
actually needed.
-Medium for biochemical reactions
CELL ORGANELLES

Specialized subunit within
the cell with specific
function.

The basic principle is that
organelle are to cell as
what an organ is to the
body

They vary in terms of
number and presence
depending on the function
and location of the cell
MEMBRANOUS ORGANELLES
They are bound by
unit membranes
similar to the cell
membrane
They are more
than the nonemembranous
organelles
1.
Nucleus
2.
Endoplasmic reticulum
3.
Golgi apparatus
4.
Mitochondria
5.
Lysosome
6.
Vacuoles
NUCLEUS
-
Largest membrane-bound organelle
-
Usually located at the center of most
cells.
-
The viscous liquid within it is called
nucleoplasm
NB: Most cell have a single nucleus
(eukaryotic), but a few cell types
have no nuclei (anucleated) and a
few others have many
(multinucleated).
FUNCTIONS OF THE NUCLEUS
 Houses
the genetic material thru its chromosome
deposit
 Control protein synthesis thru ribosome production
STRUCTURE OF THE NUCLEUS

The nucleus is surrounded by nuclear envelope/
membrane which form circular openings called
nuclear pores

The nuclear envelope consists of two
membranes;
-Inner membrane
-Outer membrane, arranged parallel to
one another.

The nuclear envelope completely encloses the
nucleus and separates the cell's genetic material
from the surrounding cytoplasm, serving as a
barrier to prevent macromolecules from diffusing
freely between the nucleoplasm and the
cytoplasm and otherwise if need be.

The outer nuclear membrane is continuous with
the membrane of the rough endoplasmic
reticulum studded with ribosome

Substances that pass through
the nuclear pore are:
1. Proteins
2. RNA (required for
gene expression and the
maintenance of
chromosomes)

Structures found within the
nuclear space are:
1. Chromosomes
(thread-like structures
made of protein and a
single molecule of
deoxyribonucleic acid
(DNA) that passes
genetic information from
parent to offsprings
2. Nucleolus
Nucleolus is the largest
structure in the
nucleus.
It assembles ribosomal
subunits to form
ribosome (protein units
of the cell)
After being produced,
the ribosome are
exported to the
cytoplasm.
ENDOPLASMIC RETICULUM
-It is a continuous
network of highly
branching tubular
membranes within
the cytoplasm.
-It can either be
*Rough ER
*Smooth ER
Rough/Granular endoplasmic reticulum is studded
with ribosome closely apposed to the nucleus
It provides a pathway for the distribution of
nuclear material into the cytoplasm.
It involves in the none-membranous
packaging of proteins/ribosome produced by
the nucleolus.
Being highly coiled in nature, it provides an
increased surface area for various mechanical
and enzymatic processes.
It forms an internal supporting framework for
the cell.
Smooth / Agranular endoplasmic reticulum lacks
ribosome.
A site of lipid and carbohydrate
synthesis
Being highly coiled in nature, it
provides an increased surface
area for various mechanical and
enzymatic processes.
It forms an internal supporting
framework for the cell.
GOLGI APPARATUS
-It is a flattened, layered, sac-like organelle.
-The apparatus is usually located close to the nucleus and ER
(where synthesis of protein, lipids and carbohydrate occurs).
-It has two surfaces; CIS and TRANS
-The Golgi body further packages/stores proteins and
carbohydrates into membrane-bound vesicles for "export".
-The Golgi apparatus gathers simple molecules from the
nucleus and ER, packages them in vesicles to either stores
them for later use or export them out of the cell.
It is also responsible for building up lysosomes (cell
digestion machines).
MITOCHONDRIA
- Most important cell organelle
-Site of energy production (ATP) for
cellular processes.
NB: Some cell lack mitochondria (red
blood cells have no mitochondria),
whereas some can have more than 2000
(liver cells)
-It is made up of two membranes;
*Outer membrane is smooth
*Inner membrane is folded into
tubular structures called
cristae.
-The matrix is the space enclosed by the
inner membrane which contain enzymes
LYSOSOMES

Are membrane bound cell organelle in the
cytoplasm containing degradative or
digestive enzymes (highly acidic fluid).

The lysosome membrane ruptures releasing
the enzymes to destroy bacteria and cell
debris.

It also brings about digestion of useful
organic substances present in the cell
(intracellular digestion).
NB: Its membranous property is necessary
because the lysosomal enzymes are capable
of destroying the entire cell, membrane are
ruptured when need arise hence commonly
described as suicide bags or time bombs of
the cell.
VACUOLES
 Are
membrane bound
storage medium of
cell.
 They
may store food
or any variety of
nutrients a cell need to
survive or waste
products so the rest of
the cell is protected
from contamination.
NON-MEMBRANOUS ORGANELLES
These are cell organelles that are not
membrane bound found closely within
the cytoplasm
1. Ribosome
2. Cytoskeleton
RIBOSOME
-Assemble proteins
from RNA codes.
-They are found free
floating in the
cytoplasm throughout
the cell or attached to
the rough endoplasmic
reticulum
CYTOSKELETON
Is a filamentous network to
maintain /change cell shape
and produce movements.
-Microfilaments are the
thinnest and most abundant
of the cytoskeleton proteins.
-Intermediate filaments
are slightly larger
-Microtubules are hollow
tubes composed of a
protein called tubulin
(biggest).
NOTE!!! SURFACE EXTENSION OF CELL
Microvilli
-Hair-like
motile
extensions on the
surface of some
cells.
-It increases surface
area for cellular
processes
 A flagellum
is a
longer lash-like
attachment that
protrudes from the
cell membrane
primarily for
locomotion.
 It
is found in
bacteria and sperm
cell
CELL TO CELL JUNCTIONS
These are
cell to cell
contact or
relationship
- Tight junction /
occluding junctions
/ zonula occludens are
closely associated areas of
two cells whose cell/
plasma membranes join
together on their lateral
surfaces.
This forms a virtually
impermeable barrier to
fluid serving as barriers of
diffusion of molecules
across the cells.
Gap junction is a
specialized intercellular
connection with
aggregates of
intercellular protein
channels within the
space across the
intercellular space.
Allows the exchange of
nutrients, ions, signals
between adjacent cells
and are also able to
communicate and
coordinate their activity.
Desmosome/
macula
adheren are
very wide
intercellular space
with proteins
embedded within
it.
The junctional
complexes contain
channels which
permit ion flows
and other
passages.
Hemidesmosome
are very small
complexes located
on the inner basal
surface of cell
connecting cell to
basement
membrane
APPLIED ANATOMY
Cell culture is the process by which
cells are grown under controlled
conditions, generally outside of their
natural environment.
Plant tissue culture, fungal culture, and
microbiological culture of microbes are
important in getting best yield on plants
and providing solution and treatment
measures on microbes.
CLINICAL ANATOMY
Cell death

Necrosis is sudden cell death which can occur as a result of
infection, injury or radiation. Necrosis is detrimental and
can be fatal

Apoptosis is programmed cell death which often provides
beneficial effects to the organism. It usually occurs during
embryonic development.
Cancerous cell grow and divide uncontrollable to
form lump (tumour) that grows in size.
Cancerous cells are malignant which grow faster
and spread to the surrounding tissues
Causes; genetic factors, lifestyle factors such
as; tobacco use, diet and physical activity,
infections and environmental exposures to
different types of chemicals and radiation.
Treatment; chemotherapy, radiation, surgery ….